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Cams, Valves and Carb matching question
Posted: Tue Jun 19, 2012 8:39 am
by scooble
I am aware that the NC35 cams are a longer duration than the NC30 ones and the valves and carbs are slightly smaller. I assume Honda designed it this way so that all the components compliment each other in order to give a good overall package of power and flexibility.
What is the effect of installing NC35 cams onto the NC30 whilst retaining the NC30 bigger carbs and valves?
Although, in theory, the cams could offer more air volume I am also aware that drop in air velocity could have negative effects on swirl and the propogation of the flame front.
In order to take full advantage of longer duration cams, would it be necessary to use a full HRC induction setup as well as a full race exhaust?
Re: Cams, Valves and Carb matching question
Posted: Tue Jun 19, 2012 11:57 pm
by lukemillar
scooble wrote:I am aware that the NC35 cams are a longer duration than the NC30 ones and the valves and carbs are slightly smaller. I assume Honda designed it this way so that all the components compliment each other in order to give a good overall package of power and flexibility.
What is the effect of installing NC35 cams onto the NC30 whilst retaining the NC30 bigger carbs and valves?
Although, in theory, the cams could offer more air volume I am also aware that drop in air velocity could have negative effects on swirl and the propogation of the flame front.
In order to take full advantage of longer duration cams, would it be necessary to use a full HRC induction setup as well as a full race exhaust?
The differences are really minimal. There is a graph floating about on here (I printed it out a while ago) and I think the only different is the exhaust duration. Intakes have the same lift/dur as the NC30.
I think the biggest thing you could change with stock cams is to slot them and to allow you to alter the timing.
Re: Cams, Valves and Carb matching question
Posted: Wed Jun 20, 2012 12:20 am
by Cammo
Valve size is the same between the engines as far as I remember.
This diagram shows the difference between vfr and rvf cams - both intake and exhaust cams are different.
Some reputable tuners on this site think that you can extract more power from the rvf engine because of bearing differences etc and other evolutions that improved rvf engine efficiency. Plenty of track bikes (including my old one) use vfr carbs on rvf engines.
Re: Cams, Valves and Carb matching question
Posted: Wed Jun 20, 2012 12:25 am
by lukemillar
Cammo wrote:Valve size is the same between the engines as far as I remember.
I thought the valves on the NC35 were smaller?
Re: Cams, Valves and Carb matching question
Posted: Wed Jun 20, 2012 12:52 am
by Cammo
I honestly can't remember, and don't have the haynes manual in front of me!
Re: Cams, Valves and Carb matching question
Posted: Wed Jun 20, 2012 2:26 am
by lukemillar
Cammo wrote:I honestly can't remember, and don't have the haynes manual in front of me!
Found this on v4power.co.uk:
Cams:
A good deal of the weight saved in the engine comes from the use of hollow camshafts. This also helps to reduce inertia. The NC35 exhaust cam is a slightly steeper profile; 1mm lift is achieved at 142-degrees, as opposed to 145-degrees on the NC30 cam (measured from 0-degrees cam angle). This will help speed up venting of the cylinder, effectively giving more opportunity for the rising piston to push out the exhaust gases. Total lift and duration are identical between engines.
The NC35’s inlet cam has a slightly longer duration; the extra 3-degrees are gained before effective opening, suggesting the cam initially opens the valve less aggressively, whilst still achieving the same total lift of 7.7mm.
Nothing on the valve size though, so I'm probably be wrong!
Re: Cams, Valves and Carb matching question
Posted: Fri Jun 22, 2012 1:51 pm
by Bike_Nut
The thing you have to remember is that the RVF mods were not in search of more power. The Japanese manufacturers had a gentlemans agreement to limit the power of the 400 class and the NC30 was already arguably above the limit. The RVF mods were aimed at boosting the midrange while keeping a similar top end, hence smaller porting/carbs
As such using the NC35 cams should help an NC30 to a tiny bit more power. I think any effect would be very small, but the lighter weight is nice as well as the gentler opening ramp on the inlet might have been to help with wear rates.
Re: Cams, Valves and Carb matching question
Posted: Fri Jun 22, 2012 2:27 pm
by scooble
V4 power.co.uk say that the inlet valve on the NC30 is 1mm dia bigger than the NC35, but the exhaust valves are the same. So it looks as far as I can see that for top end power at least, NC35 cams, pistons in an NC30 would be beneficial.
Re: Cams, Valves and Carb matching question
Posted: Fri Jun 22, 2012 9:07 pm
by lukemillar
scooble wrote:V4 power.co.uk say that the inlet valve on the NC30 is 1mm dia bigger than the NC35, but the exhaust valves are the same. So it looks as far as I can see that for top end power at least, NC35 cams, pistons in an NC30 would be beneficial.
Cams are an easy enough swap, but I would't go to the expense of changing to 35 pistons (full strip down) without doing other engine work while you're in there as I don't think the pistons alone hold enough benefit to warrant the work.
Re: Cams, Valves and Carb matching question
Posted: Sat Jun 23, 2012 12:11 am
by skinnydog0_0
The inlet valves have the same part number so i would think they are the same size??